GCN Circular 18292

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), R. L. C. Starling (U Leicester),
T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 150911A (trigger #655262)
(Starling, et al., GCN Circ. 18280
Not found
 
 
). The BAT ground-calculated position is
RA, Dec = 67.428, 5.731 deg which is
   RA(J2000)  =  04h 29m 42.6s
   Dec(J2000) = +05d 43' 50.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.

The mask-weighted light curve shows a broad peak starting around
T-2 sec and ending around T+10 sec. T90 (15-350 keV) is
T90 (15-350 keV) is 7.2 +- 0.6 sec (estimated error including systematics).

The time-averaged spectrum from T-1.04 to T+9.61 sec is best fit by a power
law
with an exponential cutoff.  This fit gives a photon index 1.02 +- 0.26,
and Epeak of 51.6 +- 3.8 keV (chi squared 52.34 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.1 +- 0.1 x 10^-06
erg/cm2
and the 1-sec peak flux measured from T+3.90 sec in the 15-150 keV band is
5.2 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.93 +- 0.05 (chi squared 97.49 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/655262/BA/